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iPhone, PocketPacket, Baofeng UV5R and APRS

I've always wanted to get into APRS. I won't detail what it is, but basically it's a digital mode that allows you to send small bits of info over your radio, in this case a Baofeng UV5R. It transmits/receives over FM on frequency 144.390. The info is passed from digipeater to digipeater, and more commonly now, over the internet as well.

It's commonly used for transmitting location (GPS), weather info, short messages, check-ins during SAR type operations, etc. The info makes it's way onto the internet, and you can track people; sort of a ham SPOT service. See http://aprs.fi or http://www.openaprs.net. A radio needs some way to get digital packets in, usually a TNC, but there are some radios with it built in. And also out, so that if a radio receives info it can send it to say your computer. But this often involves cables, the TNC (TinyTrak, etc), computer, etc.

Turns out that now there are apps for that. Like Echolink, you can use APRS with a smartphone or tablet via a couple of iOS apps (I assume there are Android ones as well). OpenAPRS lets you see stuff like on the website, and you can use the app to send your location or messages. Same with PocketPacket. Usually you have to register with a developer of the app or website admin to get an passcode to the servers; it's generated from your call sign. And bingo, anywhere you have internet you can connect and be tracked by APRS (in case NSA is ignoring you for some reason).

But what about where there's no cell, no wifi?

Unlike OpenAPRS, PocketPacket has a built in software-based TNC (sorta modem) that can send and receive data to/from your radio. So if you can hit a digipeater, you're in business.

I used it with an iPhone 5 and my UV5R. I have only got it successfully to work on the TX end (having trouble getting the right cabling in place to get data INTO the phone via its mic connection, but OUT from the phone is more important to me now; more later). Since you can use a regular 3.5mm stereo headphone plug (TRS male) into the iPhone to get music, you an also use the same to get the data (as sound, like a modem or fax squawk) OUT of the phone. The other end (same male 3.5) goes in the MIC port of the UV5R. Turn on VOX on the UV5R. On the iPhone set the path (APRS requires some setup; you can find this online but basically you tell it how to repeat your signal) and your call sign and you're pretty much in business.

A connection that will also do APRS INTO the iPhone requires more messing about since the iPhone uses a four-ring TRRS plug. Haven't got that to work yet.

Even if you aren't into tracking yourself all over, the maps I cited above are very helpful. You can click on your call sign and discover all the hops and bounces your data took, and see what stations received it. Helps in choosing repeaters if you want to switch to voice (I saw for example I would hit south of SF more reliably than stations nearer me, and that influenced which repeater I chose for voice). It also gives you access to instant weather and other stuff.

So if you've already got a iOS device, I think it's worth the $5 for the app and a couple bucks for the cable to check this out. Might come in handy.

in another posting -> http://www.qsl.net/w6dps/APRSDroid.html, he added a couple of 500 Ohm resistors. I think this basically helps step down the volume from the smart phone, so that the you don't send too strong of a signal from the smart phone into the uv5r.

the pinout also indicates where data out from the uv5r is.... this should help with getting data out of the uv5r and into the phone.

in another posting -> http://www.qsl.net/w6dps/APRSDroid.html, he added a couple of 500 Ohm resistors. I think this basically helps step down the volume from the smart phone, so that the you don't send too strong of a signal from the smart phone into the uv5r.

the pinout also indicates where data out from the uv5r is.... this should help with getting data out of the uv5r and into the phone.

I've seen that. Note that connecting the grounds (sleeve) activates PTT. This is what occurred with the first iPhone adapter I tried; the iPhone TRRS plug has a ground on the 2nd ring that connects to the sleeve of BOTH female plugs on most all adapters. http://www.ediy.co.nz/use-ipod-touch...xidc55676.html

I haven't found a way to get around that. But it works with the standard TRS cable from iPhone TO radio without any mods. The data, BTW, is coming as sound from the iPhone, and the iPhone app expects sound coming in return. I assume the data referred to in the diagram is serial data used for programming. Different things. Think of the iPhone as a modem; you can even use the speaker of the radio with the external mic of the iPhone if you wish, although it obviously has limitations.

Must be a shared PTT and audio line. That's pretty common with HTs. You have to build a little pull down circuit, nothing more than a 2K resistor and an open collector or maybe you can just get away with decoupling the audio with a cap and applying the PTT voltage with a relay.

Must be a shared PTT and audio line. That's pretty common with HTs. You have to build a little pull down circuit, nothing more than a 2K resistor and an open collector or maybe you can just get away with decoupling the audio with a cap and applying the PTT voltage with a relay.

Yeah, don't need the PTT since VOX is what the iPhone relies upon to send. That works fine. Just can't use the line-in from the phone and line-out to the phone at the same time.

Yeah, don't need the PTT since VOX is what the iPhone relies upon to send. That works fine. Just can't use the line-in from the phone and line-out to the phone at the same time.

QSL on VOX

Still confused why the line in and line out can't be used simultaneously. Just cross the pin outs and leave one of the speakers, either tip or ring 1, unused. You could mix the left and right into a mono if the iPhone doesn't have the same signal on both channels. There's only one ground connection, ring 2, on the iPhone and if you don't need PTT just decouple and add a resistor pull up to the mic line.

You might have to put a small resistor between the mic and ground to trick the device into believing that there's a mic actually present. Not sure how the controls work on top of ground and mic but I suspect they are similar to the PTT/mic sharing where one signal is AC and the other DC.

It's also important to note that Androids don't do the proprietary TRRS configuration of Apple. They put ground on the shield with ring 2 as mic. So adapters are not universal.